The present invention relates to a semiconductor device manufacturing technique and more particularly to a technique applicable effectively to a semiconductor device wherein a semiconductor chip having salient electrodes is facedown-mounted to a flexible film substrate.
In association with semiconductor devices wherein a semiconductor chip having salient electrodes such as Au bumps is facedown-mounted to a flexible film substrate there are known TAB (Tape Automated Bonding) and TCP (Tape Carrier Package).
The flexible substrate used in the aforesaid TAB or TCP generally comprises an insulating film formed by a polyimide resin for example and plural Cu leads formed on the surface of the insulating film. Therefore, it is known that there occur expansion and contraction of the insulating film due to moisture contained in the atmosphere and that an error of lead pitch results.
For example, in Japanese Published Unexamined Patent Application No. 2001-144144 it is pointed out that maintaining the humidity at 60% or so is important for preventing a change in lead pitch caused by expansion or contraction of an insulating film which is attributable to a change in humidity.
Japanese Published Unexamined Patent Application No. 2000-124255 discloses a technique of narrowing the lead pitch beforehand by the amount of an increase in lead pitch caused by expansion of an insulating film as a measure against the occurrence of an error in lead pitch which error results from expansion of the insulating film in the presence of moisture or heat contained in the atmosphere.
The present inventors are now developing a liquid crystal driver to be mounted on a liquid crystal substrate in a personal computer or a mobile communication terminal. This liquid crystal driver comprises a film substrate with Cu leads formed on the surface of an insulating film and a semiconductor chip for liquid crystal drive. The semiconductor chip is of a structure wherein it is connected to the leads of the film substrate through Au bumps.
In the step of mounting the semiconductor chip onto the film substrate, Au bumps of the semiconductor chip fixed onto a stage of a bonder and corresponding leads on the film substrate are aligned with each other, the semiconductor chip and the film substrate are sandwiched between a bonding tool heated to about 500xc2x0 C. and the stage from both above and below, followed by the application of load, thereby bonding together all of the Au bumps formed on the semiconductor chip and the corresponding leads of the film substrate.
In the above step, when the Au bumps and the leads are bonded together, the portion of the insulating film located near the leads is exposed to a high temperature and expands thermally, with consequent change in lead pitch, thus giving rise to problems such as an open defect in which the leads and the Au bumps become out of contact and a short defect in which two adjacent Au bumps are brought into contact with each other through one lead.
Particularly, in a liquid crystal driver, the number of input and output terminals is as extremely large as 500 pins or so and consequently the lead width and pitch are extremely narrow, so that there easily occurs a defective connection between the leads and the Au bumps which is ascribable to a change in lead pitch.
It is an object of the present invention to provide a technique which permits a highly accurate connection between salient electrodes of a semiconductor chip and leads of a film substrate.
Other objects and novel features of the present invention will become apparent from the following description and the accompanying drawings.
A typical invention disclosed herein will be outlined below.
A method of manufacturing a semiconductor device, comprising the steps of (a) providing a semiconductor chip, the semiconductor chip having a plurality of salient electrodes formed by conductors containing gold, (b) providing a wiring substrate, the wiring substrate comprising a thin film base formed by an insulator containing an organic resin and a plurality of leads formed on the thin film base correspondingly to the plural salient electrodes, and (c) bonding the plural salient electrodes formed on the semiconductor chip respectively to the plural leads formed on the wiring substrate, wherein, in the wiring substrate provided in the above step (b), the pitch of the plural salient electrodes is larger than the pitch of the leads at the portions corresponding respectively to the plural salient electrodes, and the plural leads are fixed to the thin film base at their portions to be bonded to the salient electrodes.